chemical?? need help interpreting. CD23 18DPO.

This current cycle I took a pregnancy test at CD16 because I had brown discharge and consecutive peak LH surges 5 days in row. I think I ovulated CD10/11. Pregnancy test showed a strong, dark positive. Took another 3 days later and it was positive but lighter and took another one today CD23 and it’s very faint.

I know it is possible a chemical pregnancy but my question is why was it a strong positive on CD16? My last cycle my period came on CD28 and later for 5 days which is normal for me. Im just confused as to why the line was so dark on CD16 like surely implantation would’ve only just occurred if egg was fertilised? So I guess my question is Could my positive test be a chemical pregnancy from last cycle or could it be something sinister like those rare tumor cysts that can spike HCG levels hence why the random brown discharge?

Photo 1 test CD16 Photo 2 test from this morning CD23.